Fluid systems, such as irrigation systems, are controlled by components, such as valves, upstream in the system. Irrigation control valves typically utilize a solenoid to open and close the valve and to ensure optimal opening and closing times. In operation, when the solenoid is off, a pilot flow path to a downstream side of the valve is closed so that flow builds pressure in a control chamber to close the valve. When the solenoid is energized, the pilot flow path to the downstream side of the valve is open, which releases pressure in the control chamber and allowing the valve to open.
The inlet and exit flow area or diameter for the pilot flow path is important. Pilot flow is the flow that enters into the control chamber, which is the area above the diaphragm, and exits the control chamber through a path to the downstream side of the valve. The path is controlled by a solenoid valve. Normally, the inlet diameter of the pilot flow path is very small and the exit diameter is larger to create a pressure differential to allow the valve to open. The inlet area, because of its small size, can be prone to clogging by external debris or mineral deposits, so it is protected by a filter. The filter helps prevent clogging due to suspended debris and dissolved solids. If the inlet port becomes clogged, the valve will not close, which leads to large amounts of fluid to continue to flow. With current filters, failures have been seen with small debris entering the filter or water containing high amounts of dissolved calcium where water settles inside the filter either on the entry or exit of the path through the filter. This latter situation occurs after the water evaporates leaving calcium carbonate deposits behind.
It is desired to have a filter that addresses the foregoing tendencies for clogging to provide a more reliable valve.